Shell-type transformer core for ballast structure



April 1965 E. scHwARz ETAL 3,177,455-

SHELL-TYPE TRANSFORMER CORE FOR BALLAST STRUCTURE Filed Aug. 8, 1961 3Sheets-Sheet 1 20 I i agf T H MW WT T H 5 24 F266 II 14 W |I g k E77x611 M H 1|! W. L /5 2 7 20 22 P321fl 4'0 Qhl f/ 1 I Z8 I H W i 1 gl'T I i 241 26 Wig 2T a0 1 1' 2g I F I k I l I" i "L 2? m MI m we UN:INVENTORS.

Q7701/vee y4 April 6, 1965 E. SCHWARZ ETAL 3,177,455

SHELL-TYPE TRANSFORMER CORE FOR BALLAST STRUCTURE Filed Aug. 8, 1961 3Sheets-Sheet 3 I W. W .H WI i} .v I, IT! H I 2 IN VENTORS.

SZZZZUMQZQQZZ United States Patent 3,177,455 SHELL-TYPE TRANSFQRMER CGREFQR BALLAST STRUCTURE Elias Schwarz and Julian Neiditch, Chicago, Ill.,assignors to Advance Transformer Co, Chicago, Ill., a corporation ofIllinois Filed Aug. 8, 1961, Saar. No. 130,170 6 Ciaims. (Cl. 336-465)This invention relates generally to ballast structures and moreparticularly is concerned with the construction of the core of a ballastintended primarily for series sequence ignition and operation of gaseousdischarge lamps.

This invention comprises an improvement upon the structure of anapplication filed by the same applicants February 2, 1961 and bearingSerial Number 86,751 granted January 8, 1963, as Patent 3,072,826.

The construction of a ballast of the type described and claimed in US.Patent 2,558,293 requires an elongate electrical steel core normallymade up of laminations of punched sheet steel stacked and assembledtogether. The basic core is known as a shell type structure in whichthere is a central winding leg on which the coils or windings aremounted side by side and there are two side legs spaced from the centralwinding leg and having yokes or bridging ends abutting the ends of thecentral winding leg and thereby providing a pair of parallel magneticflux paths with the central winding leg providing the return common toboth flux paths.

Generally the proportions of the core of these ballasts are such thatthe Width of the central winding leg is approximately twice the width ofeither of the side legs since it will be carrying approximately twicethe flux.

In order to understand generally what is involved in a series sequenceballast of the type described and claimed in US. Patent 2,558,293 it maybe said that this is basically a three winding ballast intended toignite and operate a pair of gaseous discharge lamps. The lamps igniteseriatum and after ignition operate in series. There is aprimarywinding, a first secondary winding 0r tickler, and a second secondarywinding. The primary winding is mounted in the center of the core andthe first secondary winding is mounted at one end of the core separatedfrom the primary winding by a relatively large shunt in order that therebe a very large amount of leakage reactance created during the operationor" the ballast. The second secondary winding is mounted on the otherside of the primary winding opposite the first secondary winding, alsoat the end of the core and it is normally alongside of the primarywinding sometimes separated by a shunt and sometimes abutting theprimary Winding.

When the circuit is energized one lamp which is in series with acondenser and is connected either across the first secondary windingalone or across the primary and first secondary winding together Willignite and current will flow through the condenser and first secondarywinding, thereby causing a very substantial leakage reactance to comeinto effect. The secondary windings are arranged in bucking voltagerelationship but when the large how of current occurs due to theignition of the first lamp, there will be a phase reversal of thevoltage in the secondary winding which will produce a voltage componentto combine with the voltage of the second secondary winding and ignitethe second lamp. Thereafter because of the high reactance of the firstsecondary winding, current will flow through the two lamps, thecondenser and the second secondary winding in series, substantiallybypassing the first secondary winding.

In the said Patent No. 2,558,293, the elongate iron core there shown wasconstructed of the so-called forced core variety in which the side legsand the end yokes are integral thereby providing a framing portion, andthe central Winding leg is forced into the center of the framingportion, thereby providing windows so that windings which are mounted onthe central Winding leg will fit between theside legs and the centralwinding leg.

More recently, however, the cores have been manufactured from so-calledscrapless laminations as taught, for example, in US. Patent 2,892,249and others. Such cores are punched from strips of electrical steel withmating projections and then are rearranged in such a manner that thenecessary end yokes, shunts and so forth are formed from the projectionsand notches thereby effecting great savings in material.

The invention herein is concerned primarily with the construction ofballast which is formed of the so-called scrapless laminations.

The primary object of the invention is to provide ballast structure foruse in a series sequence circuit in which the core of the transformerused in the ballast structure is formed of scrapless laminations of suchconfiguration as to provide much more efiiciency of flux flow andminimum distortion during the operation of the apparatus.

Other objects of the invention are to provide a transformer core for aballast structure which is intended to be incorporated into a seriessequence circuit in which the dies required for stamping the laminationsare simple, the structure is economical, the disadvantages normallyattendant upon the manufacture of a transformer core of this type areobviated, and the resulting ballast is quiet, cool and efiicient.

Still a further object of the invention is to provide a structure inwhich the ends of the central Winding leg are both of substantially thesame width so as to provide a rugged construction and more facile coilassembly.

Many other objects will occur as a description of preferred embodimentsappear hereinafter and it will be seen that variations can be madewithout departing from the spirit and the scope of the invention.

In the drawings:

FIG. 1 illustrates the layout of nested laminations along a strip ofsteel moving horizontally through the punch press in which dies such asprogressive dies are used to punch out the laminations.

FIG. 2 is a semi-diagrammatic sectional view taken through a transformercore constructed in accordance with the invention using the laminationswhich are stampedas shown in FIG. 1, with the laminations rearranged aswill be described.

FIG. 3 is a circuit diagram of one form of ballasting circuit of aseries sequence type.

FIG. 4 is a similar circuit diagram but showing a second form of seriessequence ballasting circuit.

FIGS. 5, 6, 7 and 8 are semi-diagrammatic views, each of which shows inits upper portion a fragmentary sectional View through a transformerusing scrapless laminations and in its lower portion the arrangement ofthe laminations nested together in the manner that they are disposed atthe time they are repetitively punched from a continuous strip of steel.

Generally, the invention herein is concerned with a method ofmanufacture and a construction of an iron core ballast in which the coreis made up of laminations of the scrapless variety punched from acontinuous strip of metal with the central winding leg and the outer orside legs nested during the punching process. The laminations are thenstacked and rearranged in such a man- Z her as to properly align thestacks to provide windows within which coils are disposed.

As mentioned previously, the primary characteristic of the structuredescribed herein is that the ends of the central winding leg are thesame width so that coils may readily be threaded upon the centralwinding leg. In the case of previous structures, the central Winding leghad a T-shaped configuration so that all of the coils or windings had tobe threaded onto the central winding leg from one end.

By a novel arrangement which will be described in detail, the centralwinding 'leg of the core described in claims hereinafter is of suchstructure as to enable the coils tobe assembled from opposite endsthereof.

In FIG. 1 there is illustrated a strip of electrical sheet steel in theprocess of passing through a punching machine, for example, and havingthe nested lamination parts punched therefrom. The strip of sheet steelis designated generally by the reference character lid, and it will beseen that a set of laminations comprising generally two outer or sidelegs 12 and a central winding leg 14 are punched in nested condition.This is a repetitious pattern along the length of the steel strip lltlso that the total scrap which results is very small. The scrap is markedS and is cross-hatched in order to enable the same clearly to be seen.

A set of laminations for a core are shown to comprise generallyelongatedE-shaped side legs 12 having lateral inward projections 16 and18 at opposite ends thereof, with a third lateral projection 20intermediate the ends thereof and a recess or notch 22 alongside theprojection 20. The central winding leg 14'; has a width A which is veryclose to two times the width'B of the side legs in order to providesuitable flux carrying capacity. The projections 20, by virtue of thenesting of the lamination parts 12 and 14, will form cut-out notches 24in the central winding leg, and the recess which is formed in the sideleg between the end projection 16 and the intermediate projection 20will comprise a. seat or window 27 whose purpose it is to accommodateone of the windings S of the ballast to be described.

The recess or notch 22 by virtue of its nesting arrangement with thecentral winding leg 14 will provide a pair of outward extensions 26 onopposite side edges of the central winding leg 14 adjacent the recesses24. The length of the central winding leg 14' and the length of the sidelegs 12 are identical except that during the punching process, by virtueof the nesting arrangement, the central winding leg is oitset from theother two extending to the right as viewed in FIG. 1 beyond the lateralprojections or extensions 18. The lateral extensions 18, therefore,notch into the central winding leg 14 and produce the recesses ornotches 28 on opposite side edges.

The dimension of these notches 28 along the length of the centralwinding leg 1'4 which is identified as C obviously will be identical tothe dimension Dof the lateral extensions l8.. It is unnecessary thatthedimension E of the end formation which will be designated'St) be thesame as the dimension D and, as a matter of fact, in order to preventthe dimension C from being excessively large, it will be found that thedimension E is normally larger than the dimension D.

Between the extension 20 and the extension18, the side members 12 willprovide an elongate seat or notch designated 32 in which the windings Pand S of the ballast to be described are adapted to be arranged.

are chosen of a suitable number of turns and size wires so that theywill be accommodated in the windows27 and SZ. The side legs, now stackedin laminatiorn'are thereafter fitted upon the assembly comprising thecentral winding leg 14 and windings in the arrangement which is shown inFIG. 2 so that the inward extensions 2% are juxtaposed relative to theoutward extensions 26, thereby forming a shunt designated as between thewinding S and the winding P. Gaps of suitable dimension are provided at355. It will be obvious that the total dimension across the resultingcore, which core is designated generally 40 in FIG. 2, is equal to Aplus two P where F is the lateral dimension of the extensions 16 and 18.The clamping notches 42 which are formed in each corner of the core maybe disregarded. If we assign the letter G to the dimension from end toend of the extensions 26 and the letter H to the width of the side legs12 at the extension 24, it will be obvious that the limitations on thedimension of G and ,H are controlled by the total dimension A plus twoF. G plus two H must equal A plus two F with slight modification to takecare of the width of the gaps 38. The depth of the notch 22 will equalone-half of G minus A. Likewise the depth K of the notch 24 is equal toH minus B.

Since the dimensions J and K are related, one can work out the necessarydimension F to accommodate a suitable width of winding which will givesatisfactory dimensions I and K for a given structure.

With respect to the notch 28, it has been found that this is desirablesince it appears beneath the winding S which is intended to carry theleading current. Wave shape is thereby improved and saturation in thecore is decreased. 7

Reference may be had to FIGS. 3 and 4 which illustrate the circuits inwhich the ballast of the type shown in FIG. 2 are intended to be used.As noted, each of these circuits usesa primary winding P, a firstsecondary winding S and a second secondary winding S In each case thewindings S and S are normally bucking on open circuit while the windingP is additive to the winding S in FIG. 4 and bucking S in FIG. 3. Linevoltage is applied across the Winding P in each case, thereby generatinga voltage in the winding S which by itself, in the case of FIG. 3, andtogether with the voltage of P in FIG. 4 is sufilcient to ignite thefluorescent lamp L in thetwo circuits. As 'soon as current flows in thelamp L and through the condenser'C, there is a phase reversal in thewinding S in each case so that there is a component of voltage which isopposite to that shown by the arrows ofthe figures. In the case of FIG.3,.tl1e voltages of P and S now combine with the component of S which isin phaserwith the voltages. of P and S and in the caseof FIG. 4, thevolt-age of S combines'with the.

component of S; which has now changed its phase so that there issufficient voltage to ignite the lamp L In The above structures areexplained in more detail in 7 US. Patent 2,558,293 and the variousrequirements for the core of such ballasts are met in the structure ofFIG.

. 2. It is required that theprirnary winding P be located Informing thecore of the ballast, assuming that the S in that order, are slipped overthe right-hand end .7

and moved along the central winding leg 14 until the winding P engagesagainst the projections 26 and the winding S abuts against the windingP. The windings in the center of the core. and separated from the othertwowindings which are arranged on opposite sides thereof. Winding S isseparated from winding P by a substantial magnetic shunt 36, and thewinding S is loosely coupled with the winding I either by a shunt or bymere side by side placement.

' The structure which has been described is advantageous in that thecore is readily formed with a minimum of scrap and is easily assembled.In the remaining figuresof the drawings, composites are shown in orderbest to illustrate the manner inwhich the modified forms are punched aswell as assembled.

In each case, below the center line the core structure is,

shown in nested condition exactly as it would be punched from a movingstrip of steel passing through a punch press. In the portions of thefigures above the center line, the core structures are shown arranged atthe time they are assembled in stack formation and provided withwindings in order to provide the necessary ballast core structures foruse with circuits of the type shown, for

sion 53% formed in the central winding leg 514. This structure differsfrom that of FIGS. 1 and 2 in the respect that it is desired that therebe an additional small shunt 556 between the windings P and S and hence,the outer legs 512' are provided with inwardly extending extension 552which because of nesting with the central winding leg 514 will give riseto the notches 554 that appear beneath the winding S As previouslyexplained, this is advantageous in that the winding S is intended tocarry a leading current and the presence of a reduced section willimprove the wave shape. In the structure of FIG. 5, during the punchingof the laminations, the central winding leg is nested to the left of theside portion 512 so that the lateral extensions 51% engage in the bodyof the central Winding leg 514 and thus provide the formation 530 at theleft-hand end substantially equivalent to the formation 3GB of FIGS. 1and 2 at the right-hand end. This means that there will be a much largernotch 528 beneath the winding 8,, and because of the need for the shunt536, cooperation between the extension 538 and the lateral extension52%) will produce an additional notch 522 in the side legs 512 outsideof the winding 8,. An additional notch 521 will be formed beneath theprimary winding P which will not have any deleterious effect. Note thatagian the width of the lateral extension 516 as indicated at D is lessthan the Width of the formation 530 as indicated at E.

FIG. 6 is a figure which is arranged similar to that of FIG. 5illustrating a ballast core 64-0 formed in a manner not much differentthan the ballast 540. The only significant difference is that instead ofa shun-t 550, Windings P and S are abutted, and in order to provide thenecessary decrease in the amount of iron beneath the winding S in orderto improve wave shape, a slot 654 is punched in the central winding leg6M. respects, the similarity is obvious.

FIGS. 7 and 8 are arranged similar to FIGS. 5 and 6 except in each casethe winding S is shown at the righthand end instead of the left. Thecores 7% and 84% are substantially longer, and in each case there is ashunt 75% and 85% formed between the windings S and P in the same manneras in the case of the core 540 in FIG. 4. These two figures illustratethe manner in which dimensions may be varied and adjusted to meetcertain requirements and conditions. Note, for example, that theright-hand end of theside legs 712 has the lateral extensions 718 muchnarrower than the opposite end lateral extensions 716. This gives riseto a notch 72% beneath the winding 8 which is much smaller than thenotch 528 of FIG. 5 and 828 of FIG. 8.

It is believed that no further explanation is necessary, and it ispointed out that the structure and method of the invention herein issimple and efiicient.

What it is desired to secure by Letters Patent in the United States is:

1. A transformer core of the shell type for a ballast structure mountinga multiple winding electro-magnetic device, said core comprising, threeparts of substantially In all other identical length cooperativelyassembled together to form the shell, each part formed of individualelectrical steel laminations stacked and arranged together to provide acentral winding leg and a pair of like side legs on opposite sides ofand parallel to the winding leg to form the side parts of the shell,inner edges of the side legs having a configuration which is a nestedconfiguration of the opposite sides edges of the central winding leg,each side eg being of elongated generally E-shaped configuration, thewinding leg having opposite ends of substantially identical width, theside legs having projections extending laterally inwardly from oppositeends thereof into abutting engagement with said opposite ends of thewind ing leg to form the bridging end parts of theshell, said windingleg and side legs having respective cooperating lateral extensionsintermediate the ends thereof facing one toward the other to divide theinterior of the shell into a pair of windows for windings to besupported on the central winding leg and to form at least one shunt onthe core.

2. A transformer core as described in claim 1 in which said side legseach has a recess in an edge thereof corresponding in linear dimensionsto the linear dimensions of the lateral extensions on the winding legand the central winding leg has recesses in opposite edges thereofcorresponding in dimensions to the lateral extensions on the side legs.

3. A tranfsormer core as described in claim 2 in which said recesses arelocated on opposite sides of and immediately adjacent said shunt.

4. A transformer core of the shell type for a ballast structure mountinga multiple winding electro-rnagnet device comprising, three parts ofsubstantially identical length cooperatively assembled together to formthe shell, each part formed of like electrical steel laminations stackedand arranged together to provide a central winding leg and a pair oflike side legs on opposite sides of and parallel to the winding leg toform the side parts of the shell, the side legs each having an inneredge the configuration of which is a nested configuration of theopposite side edge of the central leg, each side leg being of elongatedgenerally E-shaped configuration, the winding leg having opposite endsof substantially identical width, the side legs having projections ofequal width extending laterally inwardly from opposite ends thereof intoabutting engagement with said opposite ends of the winding leg to formthe bridging end parts of the shell, said Winding leg and side legshaving respective lateral extensions intermediate the ends thereoffacing one toward the other to divide the interior of the shell into apair of windows for windings to be supported-on the central winding legand'to form at least one shunt on the core, said central winding leghaving recesses in opposite edges thereof the dimensions of which areidentical to the dimensions of said projections and opening into onlyone of said windows.

5. A transformer core of the shell type for a ballast structure mountinga multiple winding electro-rnagnetic device comprising, three parts ofsubstantially identical length cooperatively assembled together to formthe shell, each part formed of like electrical steel laminations stackedand arranged together to provide a central winding leg and a pair oflike side legs on opposite sides of and parallel to the winding leg toform the side parts of the shell, the side legs each having an innerlongitudinal edge the configuration of which is a nested configurationof the opposite longitudinal edge of the central leg, each side legbeing of elongated generally E-shaped configuration, the winding leghaving opposite ends of substantially identical width, the side legshaving projections extending laterally inwardly from opposite endsthereof into abutting engagement with said opposite ends of the windingleg to form the bridging end parts of the shell, said winding leg andside legs having respective lateral extensions intermediate the endsthereof facing one toward the 3 other to divide the interior of theshell into a pair of windows for windingsto be supported on the centralwinding leg and to form at least one shunt on the core,

the linear width across the lateral extensions of said winding leg andtwice the width of a side leg at the lateral extension thereof beingapproximately equal to device comprising three parts of substantiallyidentical length cooperatively assembled together to form the shell,

'shapedconfiguration, the Winding leg having opposite ends ofsubstantially identical width, the side legs having projectionsextending laterally inwardly from opposite ends thereof into abuttingengagement with said opposite ends of the winding leg to form thebridging end parts of the shell, said winding leg and side legs havingrespective lateral extensions intermediate the ends thereof facing onetoward the other to divide the interior of the shell into a pair ofwindows of different dimension considered along the length of the corefor windings to be supported on theoentral winding leg and to form atleast one shunt on the core, each of said windows arranged to have awinding supported therein intimately engaged against said facingextension ends.

References Cited in the file of this patent UNITED STATES PATENTS2,509,188 Feinberg May 23, 1950 2,510,209 Bridges June 6, 1950 2,671,951Sliwiak Mar. 16, 1954 2,734,176 Gould et a1. Feb. 7, 1956 2,892,249Feinberg et al. June 30, 1959 2,958,931 Hurt Nov. 8, 1960 3,003,081Huberty et a1 Oct. 3, 1961 3,010,050 Hume et a1 Nov. 21, 1961 3,010,185Hume Nov. 28, 1961 Feinberg 'Aug. 21, 1962

1. A TRANSFORMER CORE OF THE SHELL TYPE FOR A BALLAST STRUCTURE MOUNTINGA MULTIPLE WINDING ELECTRO-MAGNETIC DEVICE, SAID CORE COMPRISING, THREEPARTS OF SUBSTANTIALLY IDENTICAL LENGTH COOPERATIVELY ASSEMBLED TOGETHERTO FORM THE SHELL, EACH PART FORMED OF INDIVIDUAL ELECTRICAL STEELLAMINATIONS STACKED AND ARRANGED TOGETHER TO PROVIDE A CENTRAL WINDINGLEG AND A PAIR OF LIKE SIDE LEGS ON OPPOSITE SIDES OF AND PARALLEL TOTHE WINDING LEG TO FORM THE SIDE PARTS OF THE SHELL, INNER EDGES OF THESIDE LEGS HAVING A CONFIGURATION WHICH IS A NESTED CONFIGURATION OF THEOPPOSITE SIDES EDGES OF THE CENTRAL WINDING LEG, EACH SIDE LEG BEING OFELONGATED GENERALLY E-SHAPED CONFIGURATION, THE WINDING LEG HAVINGOPPOSITE ENDS OF SUBSTANTIALLY IDENTICAL WIDTH, THE SIDE LEGS HAVINGPROJECTIONS EXTENDING LATERALLY INWARDLY FROM OPPOSITE ENDS THEREOF INTOABUTTING ENGAGEMENT WITH SAID OPPOSITE ENDS OF THE WINDING LEG TO FORMTHE BRIDGING END PARTS OF THE SHELL, SAID WINDING LEG AND SIDE LEGSHAVING RESPECTIVE COOPERATING LATERAL EXTENSIONS INTERMEDIATE THE ENDSTHEREOF FACING ONE TOWARD THE OTHER TO DIVIDE THE INTERIOR OF THE SHELLINTO A PAIR OF WINDOWS FOR WINDINGS TO BE SUPPORTED ON THE CENTRALWINDING LEG AND TO FORM AT LEAST ONE SHUNT ON THE CORE.